1. Field of the Invention
The present invention relates to a wire electric discharge machine performing turning tool machining, a turning tool machining method with a wire electric discharge machine, and a program creation apparatus for a wire electric discharge machine that performs turning tool machining.
2. Description of the Related Art
Cases of machining a turning tool with a wire electric discharge machine have been increased in recent years (refer to Japanese Patent Application Laid-Open No. 9-267219). Especially, an object to be machined made of a hard material such as a polycrystalline diamond (PCD) tool and a polycrystalline cubic boron nitride (PCBN) tool can discharge electricity so as to be able to be machined in higher speed than machining with a grinding machine of prior art and be machined intricately with a single-shaped tool (that is, a wire electrode). Therefore, a case of machining the tools with a wire electric discharge machine has been increased.
A PCD tool and a PCBN tool are manufactured such that a PCD member and a PCBN member are cut out from a PCD material and a PCBN material in forms of tips as materials of a cutting tool, a brazing material is melted with a high frequency induction device, the tip obtained by the cutting is brazed on a shank as a cutting blade (referred to below as a “half-completed turning tool”), and the obtained piece is machined into a final shape so as to obtain a turning tool which is a completed product.
In a brazing process, a tip is positioned and fixed in a manner to interpose melted wax, so that it is hard to fix the tip on an ideal position on design without any error. Further, due to an effect of heat in brazing and unevenness of the thickness of a tip itself, waviness is frequently formed on a rake face. Consequently, a rake face of a half-completed turning tool frequently obtains a shape having an error in no small measure compared to an ideal shape on design (refer to FIGS. 5A and 5B).
In a case where the shape of a rake face is different from an ideal shape, when a machining route prepared on the basis of an ideal shape is used as it is, an error in a height direction of an actual rake face with respect to an ideal rake face adversely affects shape accuracy of an object to be machined, generating an error that is unignorable in producing of a highly-precise object. Commonly, in order to eliminate such error, a shank is fixed on a jig for which the inclination can be adjusted, a tip is inclined so that a rake face becomes closest to an ideal shape, and then machining is performed.
Thus, a jig for inclining and adjusting a tip and the process for adjusting inclination are required. Further, in a case where “waviness” is formed on a rake face, an error cannot be completely eliminated even by adjusting inclination of the rake face, generating an error on a machined blade.
Further, a tip surface is inclined, so that a reference face of a turning tool (commonly, a bottom face) is also inclined and the tip is machined into a final shape in such state. Therefore, when the tip is actually fixed on a lathe or the like and used, such complicated operation that the tip is fixed on a tool rest with the reference face thereof inclined is required, in a similar manner to turning tool machining, and similar adjustment is required every time a turning tool is exchanged.
Thus, in the conventional machining method, the number of processes is increased in both of manufacturing and a use of a turning tool, and it is hard to produce a precise blade depending on a property of a rake face.